1. Field of the Invention
The field of the invention relates generally to solid state motor actuators. More particularly, the invention relates to integral connectors for piezoelectric solid state motor stacks.
2. Related Art
For decades electroexpansive materials have been employed in stacked structures for producing actuation used for fuel injection and valve control in diesel engines, for example. Commercially manufactured solid state motor stacks, or actuators, are produced using piezoelectric disks interleaved with metal foil electrodes. Application of high voltage and resulting high peak current power to alternately biased electrodes causes each of the piezoelectric disks to expand or axially distort. The additive deflection of the stacked disks is typically amplified by hydraulics to effectuate useful actuation.
An example of a conventional electromechanical actuator having an active element of electroexpansive material is found in U.S. Pat. No. 3,501,099 to Glendon M. Benson. Benson's 1970 patent is directed to both an actuation amplification structure and a method for manufacturing piezoelectric stacks. Sheets of ceramic material are rolled, compacted and punched into ceramic disks. After a cleaning process, the disks are stacked with alternate sets of continuous disk electrodes disposed between the ceramic disks. The stacks undergo a pressurized cold-welding process, followed by an elevated temperature and pressure bonding process after common electrodes are connected to the two electrode groups. The stacks are poled by application of a DC voltage and then encapsulated with a plastic insulative cover prior to final mounting within a transducer housing.
Conventionally, and as mentioned above, stacks are connected to high voltage power supplies for application of driving voltages to produce actuation. Connection of the driver to the stack is problematic, however, due to the environments in which stacks are used. Mounting of stacks on engine heads, for example, exposes stack/driver connectors and accompanying wiring harnesses to high temperatures, powerful resonant vibrations and, at times, corrosive agents such as diesel fuel and engine cleaners.
Many high voltage electrical connectors have been developed for use in such harsh environments, but none have yet been designed or adequately adapted for use with piezoelectric solid state motor stacks.
The present invention overcomes the deficiencies of the conventional technology noted above.